Abstract:
Water and microbial mat communities of the ponds in the Labyrinth area of Wright Valley was investigated to test the hypothesis that the gradient in climatic severity associated with latitudinal and altitudinal gradients drives a corresponding gradient of biological diversity and productivity. The biological, physical and chemical parameters of 12 ponds were sampled in mid-January. Aspects of the ... water column were measured to describe depth related changes in temperature, conductivity, dissolved oxygen, pH, redox potential and a fine scale profile (10cm depth intervals) of water samples was analysed for major ions in relation to changes in conductivity with depth and between ponds. Aspects of biology analysis were for phytoplankton chlorophyll a, PNPP, PNPC and dissolved nutrients. Microbial mat samples were taken for species composition and biomass. Photosynthesis vs irradiance experiments were conducted on microbial mats in two ponds to ascertain the acclimation to the ambient light environment. In a few cases, ephemeral ponds were found that had dried up completely with salts precipitated out and samples were collected for later identification by x-ray diffraction. The following season, the same ponds were sampled in mid-October specifically to collect samples of the highly saline basal brine which occurs below the ice of the predominantly frozen pond over winter. Temperature, conductivity, pH and dissolved oxygen concentration were measured at various depths. Basal brine and melted ice samples were analysed for major ions and nutrients and trace metals. Salt precipitations were collected from various dry evaporate basins. Ice cores were collected from one pond for analysis of salt content, salt inclusion, ice structure and dissolved gases.